Cleaning Foggy Double-Pane Windows

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Sharolyn asked: How do I clean a double pane patio door? We recently placed an old camper on the back of our property, in the woods, to enjoy on weekends. The patio door has become so foggy on one section that we cannot see through it. We do not care if it is sealed or now, but would like to be able to sit inside and see out. How can we get to the inside of the door to clean it?

Double pane doors and windows consist of two panes of glass with a space between them. This bit of insulating air space increases the R value of the window, but it’s also prone to fogging, especially in older units or ones that withstand a lot of abuse from the elements. Fogging results when the seal fails or is compromised in any way, allowing moisture to seep through the barrier and into the space between the glass. Seal failure can occur with too much heat (when the seal softens and expands) or in cold temperatures (when it hardens and becomes brittle).

Once the seals fail and fogging begins, there’s no practical way to repair it. Theoretically, you would have to separate the panes of glass, clean and thoroughly remove all moisture, then reattach and seal them. Doing so without trapping any humidity is improbable, if not impossible, and then you need to replicate a factory-quality seal without breaking or damaging the glass. Therefore, the only effective way to rid your view of the fogging is to replace the door.


If you opt to remove the seal to clean the door, be aware that the problem will quickly reoccur. While the initial cleaning will remove the dirt temporarily, the lack of a seal will cause the door to fog over and collect dirt much quicker. Some say to remove one of the panes so that it becomes a single-pane door. However, the fixtures are not designed for this and the single pane will fit loosely in the fixture. This makes it more prone to breaking and damage.

If you choose to remove the panes and the seal for cleaning, consult your owner’s manual or manufacturer for the proper method to remove the glass panes. All doors are designed differently, and the disassembly steps are not the same for each door type. Still, consider replacing the door with a low-cost single pane door, and you will have both a better view and stronger fixture.

Newer technology has reduced the failure rate of properly installed double pane doors to 1% after 10 years and 3% after 15 years, so your investment should be a lasting one. To increase the lifetime of your new double pane doors, keep the following in mind:

  • Purchase glass with a long warranty. This generally means a higher quality product, and if not, a premature failure is a covered repair.
  • Inspect your glass periodically. Look for the seals to be in good shape. Any splits, cracks, or other deterioration is a warning sign that failure, and condensation or fogging, may be in your future.
  • Keep glass clean and ensure good circulation around it. If dirt and moisture are allowed to build and remain on the outer surfaces, they will wear away at the seals and may speed up the process of failure.

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